Liquid pump

ABSTRACT

The invention relates to a liquid pump having a pump housing, a pump unit for generating a pilot pressure, a drive shaft used to drive the pump unit and guided out of the pump housing on a drive/output side, and a sealing unit sealing the passage. When the liquid pump is subjected to an admission pressure, the pressurized liquid generates, in the region of the sealing unit, at least one pressure field facing the sealing unit and at least one pressure field facing away from the sealing unit. According to the invention, an asymmetrical arrangement of the pressure fields is provided.

PRIOR ART

The invention relates to a liquid pump as generically defined by the preamble to independent claim 1.

Typically, liquid pumps embodied as geared pumps, comprise a rotatably disposed drive shaft, which leads into a pump housing of the liquid pump. In the pump housing, there is a pump unit with at least one gear wheel that performs the pumping function. The drive shaft is ducted on only one side of the pump housing and transmits driving energy to the at least one gear wheel. This duct must be sealed off with a sealing unit, embodied for instance as a radial shaft sealing ring. If the liquid pump generates an operating pressure p_(B), or if the liquid pump is loaded with pilot pressure p_(V), this sealing unit absorbs the resultant axial load in that the sealing unit seals off the pump housing from the environment. This axial load F is calculated from the sealing diameter D of the shaft and the pilot pressure p_(V) applied in accordance with the equation F=p_(V)*D²*π/4.

For example, German Patent Disclosure DE 199 24 057 A1 shows a liquid pump with a pump housing and a pump unit, disposed in the pump housing, for generating an operating pressure of the liquid. For driving the pump unit, a drive shaft ducted on a driving/driven side from the pump housing is provided, which is supported in the pump housing via bearing units. The duct is sealed off via a sealing unit. On loading of the liquid pump, the liquid that is under pressure, in the vicinity of the sealing unit, generates at least one pressure field oriented toward the sealing unit and at least one pressure field facing away from the sealing unit at the sealing unit.

DISCLOSURE OF THE INVENTION

The liquid pump of the invention is defined by the characteristics of independent claim 1 has the advantage over the prior art that an asymmetrical disposition of the pressure fields is provided. Thus the faces loaded by the pilot pressure are of different sizes. By means of an asymmetrical disposition of the pressure fields affecting the pilot pressure, the axial force in the liquid pump that is created upon loading of the liquid pump with the pilot pressure can be compensated for. A force equilibrium is created at the drive shaft. The bearing units of the liquid pump need to absorb only radial forces, which leads to simplification of the bearing units and resultant cost savings. Advantageously, there is a reduction in the pressure load on the sealing unit. Because the sealing unit now needs to absorb only lesser pressures, the sealing unit can be designed in a markedly less expensive way.

Advantageous improvements to the liquid pump defined by the independent claim are possible by means of the provisions and refinements recited in the dependent claims.

To obtain an asymmetrical disposition of the pressure fields, preferably the pressure field oriented toward the sealing unit is larger than the pressure field facing from the sealing unit. The result is optimal sealing off of the pump housing from the environment. If the pump unit has a plurality of gear wheels, the area of the pressure fields can be distributed among the individual gear wheels.

Especially advantageously, the pressure field oriented toward the sealing unit is larger, by the area of the cross section of the drive shaft, than the pressure field facing away from the sealing unit.

Advantageously, an enlargement of the pressure field oriented toward the sealing unit can be attained simply and economically by way of an indentation in a sealing face of the liquid pump. Thus the faces loaded by the pilot pressure are of different sizes. This creates a pressure-free area opposite the sealing unit.

Preferably, a symmetrical disposition of the pressure fields that are referred to an operating pressure of the liquid pump is provided. As a result, in cooperation with the pressure fields of the pilot pressure, a force equilibrium results at the drive shaft.

Because the pressure field of the pilot pressure facing away from the sealing unit is designed as smaller than the pressure field oriented toward the drive shaft, and the pressure fields of the operating pressure are designed symmetrically, the pressure-free area is created opposite the sealing unit. To relieve this pressure-free area in a simple and economical way, a conduit for connecting the indentation with a chamber in the pump unit is preferably provided.

The pump unit is a toothed gearing. Advantageously, the chamber in the pump unit is a chamber between the teeth of two gear wheels, that is, in so-called tooth gaps. Preferably, the tooth gaps directly after the apex point are used, as a result of which because of the extent of the gaps, an underpressure is created.

Also, for relieving the pressure-free area, a line for connecting the indentation with a storage chamber can be provided, which again makes a simple, economical realization of relief possible.

Advantageous embodiments of the invention are shown in the drawings and will be described below. In the drawings, the same reference numerals indicate components and elements that perform the same or analogous functions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic longitudinal section through a liquid pump of the invention.

FIG. 2 shows a schematic cross section through the liquid pump.

EMBODIMENTS OF THE INVENTION

FIG. 1 shows a liquid pump 10 of the invention in the form of a geared pump, with a pump housing 12 that has an inner chamber 46, with an inlet 48 from an intake side, and an outlet 50 on a compression side. A rotatably disposed drive shaft 16 leads into the pump housing 12 via a shaft duct to be sealed off, and the drive shaft drives a pump unit 14 disposed in the inner chamber 46 of the pump housing 12.

The pump unit 14 serves to deliver the liquid, generating a suitably high pressure level of the liquid, or in other words generating an operating pressure p_(B). The liquid is pumped in the usual way from the intake side to the compression side of the liquid pump 10. To that end, the pump unit 14 preferably has a toothed gearing, which as a rule includes at least two gear wheels 38, 40 shown in FIG. 2, of which one is driven via the drive shaft 16. Depending on the disposition and size of the gear wheels, this may preferably be an external geared pump, inner geared pump, tooth ring pump, or helical pump. As a rule, the liquid pump 10 uniformly delivers the liquid to be pumped. There is a symmetrical disposition of the pressure fields 30, 32 of the operating pressure p_(B).

The drive shaft 16 is supported rotatably in the pump housing 12 via bearing units 52, 54. Between the shaft duct and the drive shaft 16, there is a sealing unit 18, embodied as a shaft sealing ring, for sealing off the pump housing 12 at the drive shaft 16 from the outside or from the environment. The shaft sealing ring 18 is disposed with a fixed seat in a recess in the pump housing 12. Preferably, the shaft sealing ring 18 is embodied as a radial shaft sealing ring, which presses radially on the surface of the drive shaft 16. The shaft sealing ring 18 must be designed in accordance with a pilot pressure p_(V) that can be applied to the liquid pump 10 and the operating pressure p_(B) that occurs in the pump housing 12; that is, depending on the pressure level, the shaft sealing ring 18 must exert adequately high radial forces to perform its function. On loading of the liquid pump 10 with the pilot pressure p_(V), the liquid under pressure in the vicinity of the sealing unit 18 generates at least one pressure field 20 oriented toward the sealing unit 18 and at least one pressure field 22 facing away from the sealing unit 18 at the sealing unit 18.

To compensate for the axial force F, caused by the pilot pressure p_(V), directly in the liquid pump 10, according to the invention an asymmetrical disposition of the pressure fields 20, 22 is provided. In the present exemplary embodiment, the pressure field 20 oriented toward the sealing unit 18 is larger than the pressure field 22 facing away from the sealing unit 18. Preferably, the pressure field 20 oriented toward the sealing unit 18 is larger, by the area of the cross section 24 of the drive shaft 16, than the pressure field 22 facing away from the sealing unit 18.

Enlarging the pressure field 20 oriented toward the sealing unit 18 is achieved as shown in FIG. 2 via an indentation 26 in a sealing face 28 of the liquid pump 10. For relieving this indentation 26, which forms a pressure-free area, a conduit 34 is provided for connecting the indentation 26 with a chamber 36 in the pump unit 14. Preferably, the chamber 36 in the pump unit 14 is a chamber between the teeth of the two gear wheels 38, 40. Also, in addition to the relief of the pressure-free area 26 embodied as an indentation, a line 42 is provided for connecting the indentation with a storage chamber 44. It is understood that these provisions for relief may be provided individually instead. 

1-9. (canceled)
 10. A liquid pump, having a pump housing, a pump unit generating an operating pressure, a drive shaft being ducted out of the pump housing on a driving/driven side for driving the pump unit, and a sealing unit sealing off the duct, in which when the liquid pump is loaded by a pilot pressure, the liquid under pressure, in the region of the sealing unit, generates at least one pressure field of the pilot pressure oriented toward the sealing unit and at least one pressure field of the pilot pressure facing away from the sealing unit at the sealing unit, wherein the pressure fields of the pilot pressure have an asymmetrical disposition with respect to one another.
 11. The liquid pump as defined by claim 10, wherein the pressure field oriented toward the sealing unit is larger than the pressure field facing away from the sealing unit.
 12. The liquid pump as defined by claim 10, wherein the pressure field oriented toward the sealing unit is larger, by the area of the cross section of the drive shaft, than the pressure field facing away from the sealing unit.
 13. The liquid pump as defined by claim 11, wherein the pressure field oriented toward the sealing unit is larger, by the area of the cross section of the drive shaft, than the pressure field facing away from the sealing unit.
 14. The liquid pump as defined by claim 10, further having an indentation in a sealing face of the liquid pump.
 15. The liquid pump as defined by claim 11, further having an indentation in a sealing face of the liquid pump.
 16. The liquid pump as defined by claim 13, further having an indentation in a sealing face of the liquid pump.
 17. The liquid pump as defined by claim 10, further having pressure fields of the operating pressure which have a symmetrical disposition relative to one another.
 18. The liquid pump as defined by claim 16, further having pressure fields of the operating pressure which have a symmetrical disposition relative to one another.
 19. The liquid pump as defined by claim 14, further having a conduit for connecting the indentation with a chamber in the pump unit.
 20. The liquid pump as defined by claim 16, further having a conduit for connecting the indentation with a chamber in the pump unit.
 21. The liquid pump as defined by claim 18, further having a conduit for connecting the indentation with a chamber in the pump unit.
 22. The liquid pump as defined by claim 10, wherein the pump unit comprises a toothed gearing.
 23. The liquid pump as defined by claim 21, wherein the pump unit comprises a toothed gearing.
 24. The liquid pump as defined by claim 19, wherein the chamber in the pump unit is a chamber between teeth of two gear wheels.
 25. The liquid pump as defined by claim 20, wherein the chamber in the pump unit is a chamber between teeth of two gear wheels.
 26. The liquid pump as defined by claim 21, wherein the chamber in the pump unit is a chamber between teeth of two gear wheels.
 27. The liquid pump as defined by claim 14, further having a line for connecting the indentation with a storage chamber.
 28. The liquid pump as defined by claim 15, further having a line for connecting the indentation with a storage chamber.
 29. The liquid pump as defined by claim 16, further having a line for connecting the indentation with a storage chamber. 